The majority of costs and suffering attributed to Type II Osteoporosis results from the incidence of hip fractures. We propose to examine the architecture of the proximal femur in high risk and low risk subjects, evaluating both gross regional density patterns and microscopic structural properties. Using appropriate cadaver material (50 pairs of proximal femurs), we propose to establish the biomechanical significance (both static and fatigue strength) of regional bone density obtained from two measurement methods; dual energy x-ray densitometry, and fine detail QCT. Further, the ability of these measurements to discriminate between 50 subjects at an increased risk of fracture (patients who recently sustained their first hip fracture) and an age and sex matched control group (n = 50) will be demonstrated. The performance of mechanical models derived from measured density (2D beam and 3D finite element) will also be evaluated. Simultaneously, a limited number of biopsies will be obtained from the fracture site of a subset (20) of patients (during surgical arthroplasty) and from a matched set of the anatomic specimens. The micro-structural architecture of femoral bone tissue will be evaluated using micro- computed tomography and scanning electron microscopy. In this way, we intend to improve bone measurement methods at the hip and verify their significance in both biomechanical and clinical environments. Any increase in sensitivity resulting from the development of the mechanical models will also be recorded. Ultimately, a relative risk analysis will provide clinicians with the data useful in appropriately treating and counseling their elder patients. Additionally, data regarding the trabecular architecture may yield clues to the development, and thus treatment, of Type II Osteoporosis.